What is the virtual button click event and click the virtual check box of the web form login ?

I have got Login web code: http://dotnetlearners.com/blogs/create-simple-login-page-in-html-using-css
The problem here when running I want to execute commands in this virtual login button or virtual checkbox, I have to declare how the event btnLogin_Click (..) runs in LogIn.aspx.cs file? The same for virtual checkboxes.

[CODE]

protected void btnLogin_Click(object sender, EventArgs e)
    {
        //Open web Registration.aspx
        Response.Redirect("Registration.aspx");
    }

[/CODE]